Protocol to measure human IL-6 secretion from CAR T cell-primed macrophage and monocyte lineage cells in vitro and in vivo using humanized mice

Chimeric antigen receptor (CAR) T cell therapy often causes serious toxicities, such as cytokine release syndrome (CRS), mainly due to interleukin-6 (IL-6) secreted by monocyte lineage cells. Here, we describe a protocol to generate anti-CD19 CAR T cells and quantify human monocyte-derived IL-6 cocultured with CAR T cells and target tumor cells in vitro. We further describe a protocol to generate a humanized mouse model and evaluate CAR T cell-associated plasma IL-6 levels in vivo. For complete details on the use and execution of this protocol, please refer to Yoshikawa et al.1.